How can I find out a whois server for a particular domain?

Question

I'm trying to make a desktop application checking whois records among other things and I've found a few lists mapping top-level domains to whois servers. They work usually, but sometimes information has to be found on a different whois server. For example while the main server for com domains is whois.markmonitor.com, about.com has to be fetched from "corporatedomains". How do I check which whois server should I query for a certain domain?

Answer 1

There are two kind of WHOIS servers: Thin and thick.

From Wikipedia

WHOIS information can be stored and looked up according to either a thick or a thin data model:

Thick

one WHOIS server stores the complete WHOIS information from all the registrars for the particular set of data (so that one WHOIS server can respond with WHOIS information on all .org domains, for example).

Thin

one WHOIS server stores only the name of the WHOIS server of the registrar of a domain, which in turn has the full details on the data being looked up (such as the .com WHOIS servers, which refer the WHOIS query to the registrar where the domain was registered).

Thick WHOIS servers are available on the IANA website. For example, here's the IANA record for the IT TLD.

Scroll down to

WHOIS Server: whois.nic.it

Thin servers are a little bit more complicated. You need to query the main WHOIS server (available on IANA), then extract the referral.

For example, here's the record for example.com. The response from Verisign (the first .COM WHOIS server) returns some information including the Whois Server.

Server Name: EXAMPLE.COM.AU
Registrar: ENETICA PTY LTD
Whois Server: whois.enetica.com.au
Referral URL: http://www.enetica.com.au

Then you need to extract the WHOIS server and run a second query.

A list of all available WHOIS servers is included in my Ruby Whois project. Check the definitions folder.